It's a brief commentary on Tozan's Five Ranks, relating them to actualization of the Four Wisdoms/Three Bodies. It describes Zen's gate which is the recognition of one's own Dharmakaya wisdom (kensho/Great Perfect Mirror Wisdom), the subsequent actualization of Sambhogakaya (i.e. embodiment/integration through practice of the Jewel Mirror Samadhi, which is fulfillment of the Universal Nature Wisdom), and finally Nirmanakaya as the free functioning within activity (fulfillment of the Marvelous Observing Wisdom and Perfecting-of-Action Wisdom).

A quote from the Sixth Patriarch in that text sums all of this up: "The pure Dharmakaya is your nature; the perfect Sambhogakaya is your wisdom; the myriad Nirmanakayas are your activities".

~ Meido

Nowadays there is much talk about the sublime and the profound, or conversely criticism of the Two Vehicles, belittling their authority. [Proponents of] the partial, the round, the exoteric and the esoteric schools contend with each other, yet they have not even accomplished the confirmation of the Two Vehicles, let alone that of the Bodhisattva Vehicle. And as for the One Buddha Vehicle, how could they conceive of it even in their dreams? What use to them are the partial, round, exoteric and esoteric teachings? - Torei

It's a brief commentary on Tozan's Five Ranks, relating them to actualization of the Four Wisdoms/Three Bodies. It describes Zen's gate which is the recognition of one's own Dharmakaya wisdom (kensho/Great Perfect Mirror Wisdom), the subsequent actualization of Sambhogakaya (i.e. embodiment/integration through practice of the Jewel Mirror Samadhi, which is fulfillment of the Universal Nature Wisdom), and finally Nirmanakaya as the free functioning within activity (fulfillment of the Marvelous Observing Wisdom and Perfecting-of-Action Wisdom).

A quote from the Sixth Patriarch in that text sums all of this up: "The pure Dharmakaya is your nature; the perfect Sambhogakaya is your wisdom; the myriad Nirmanakayas are your activities".

Soto zen tradition is very specific about trikaya - it is dharmakaya of Vairochana, sambhogakaya of Vairochana and nirmanakaya of Shakyamuni. This is an axis of dharma transmission in soto. Moreover trikaya is used in 100 day retreat practice of rishubun, and all rituals related to it. This is practice only after the dharma transmission.